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CRD Loss Meter and Reflectometer


Cavity-Ringdown (CRD) Loss Meter and Reflectometer

Our reflectometer GLACIER uses the extreme sensitivity of cavity ring-down spectroscopy to 

quantify the losses of advanced optical coatings down to 5 ppm. As a typical application the 

device can characterize supra-mirrors with up to 99.9995 % reflectivity. Conventional 

absorption and reflection measurements are not sufficiently sensitive to quantify today´s 

super-reflective mirror coatings and are typically limited to the > 1000 ppm range 

(corresponding to < 99.9 % reflectivity). Cavity ring-down spectroscopy measures optical

losses by the decay of the energy stored inside a cavity. The technique reaches unrivalled 

sensitivity, because losses are experienced with each round trip inside the cavity over and over 

again. Smaller losses lead to longer intra-cavity dwell time thereby automatically increasing 

measurement precision. The device features high-speed data acquisition and allows to record 

measurements within seconds. It is delivered complete with a computer and a user-friendly 

software interface for acquisition and real-time analysis.


Key Product Features

  Reflectivity measurements up to 99.9995%

  Various angles of incidence: 5°-45° (and 0°)

  S and p polarization (separately)

  Antireflective coating characterization down to 0.0005% (5 ppm)

  Simple and reproducible alignment for 0.5”, 1” and 2” optics

  Spring-loaded mirror fixtures for reproducible mounting without strain

  Computer and user-friendly software interface included

  High-speed data acquisition and real-time analysis

  Wavelengths in the range 375-1550 nm available

  Footprint 90 x 45 cm²

 Number of wavelengths one  two three
 Wavelength range                                                                         375-1550 nm
 Footprint 90 x 45cm2 90 x 55cm2


Working Principle

Glacier uses the principle of reflectivity/loss measurements with cavity ring-down spectroscopy based on very low losses at each mirror bounce. 

The laser pulses travel inside a cavity experiencing optical losses over and over again during each round trip.


Sketch of the working principle of GLACIER, measurement and fitting procedure

Sample Measurement


The device measures the time-dependent intensity I(t) leaked through an end mirror 

of the cavity (center). 

The signal decays with a time constant depending on the intra-cavity losses and can

be fitted to the following exponential function:


The time constant τ is inversely proportional to the optical losses (1-R) of the cavity 

withtotal reflectivity R:


where n is the refractive index, c is the speed of light, and l is the cavity length

Typical GLACIER measurement of an ultrahigh-reflective mirror for 1030 nm. 

To obtain the data, the cavity losses with and without the sample were 

measured and subtracted. This provides an absolute measurement 

of the test mirror

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Compare Model Drawings & Specs Availability Reference Price